Field of the Invention and Description of the Prior Art
This invention relates to an improved thermoplastic coated paperboard container of the type having a gabled top and pouring spout for a liquid contained therein, provided in the top closure thereof, and the invention particularly relates to such a liquid storage container wherein the top closure is formed or is formable into a substantially flattened or partially flattened condition.
Paperboard cartons having a thermoplastic coating thereon for containing liquids have been widely used for many years. Probably the most widely used of these cartons is the "gable top" type of container which includes a unitarily formed pouring spout in the top closure thereof. Examples of thermoplastic coated paperboard containers of the "gable top" type are:
Arslanian U.S. Pat. No. 3,232,516 PA1 Arslanian U.S. Pat. No. 3,239,126 PA1 Braun U.S. Pat. No. 3,498,524 PA1 Crawford U.S. Pat. No. 3,116,002 PA1 Crawford U.S. Pat. No. 3,185,376 PA1 Crawford U.S. Pat. No. 3,291,369 PA1 Crawford U.S. Pat. No. 3,334,799 PA1 Crawford U.S. Pat. No. 3,471,076 PA1 Egleston U.S. Pat. No. 3,120,335 PA1 Egleston U.S. Pat. No. 3,270,940 PA1 Egleston U.S. Pat. No. 3,406,892 PA1 Egleston U.S. Pat. No. 3,474,951 PA1 Huang U.S. Pat. No. 3,319,868 PA1 Huang U.S. Reissue No. 26,305 PA1 McNair U.S. Pat. No. 3,365,111 PA1 Miller U.S. Pat. No. 3,294,310 PA1 Miller U.S. Pat. No. 3,412,922 PA1 Pike U.S. Pat. No. 3,365,115 PA1 Schwenk U.S. Pat. No. 3,654,842 PA1 Seiple U.S. Pat. No. 3,120,333 PA1 Thomas U.S. Pat. No. 3,185,375
Containers of this type, generally disclosed in the foregoing patents, all of which are the "gable top" type, have a unitarily formed pouring spout stored within the gable top and have been widely used and widely accepted. However, recently efforts have been directed towards folding down the gable top of these containers to provide a flat top end closure. Such flat top end closures are shown, for example, in Egleston Design Pat. No. 235,515, in Braun U.S. Pat. No. 3,869,078, and in Egleston U.S. Pat. No. 3,892,347. The purpose of the flat end closure containers is to provide for easier stacking of the containers, such as in dairy shipping cases and in refrigerated grocery display cases and for reducing the storage and/or shipping volume required for such containers in each size.
One flat top end closure container that has been used generally comprises a top closure which is generally formed in a manner similar to the gable top construction, except that there are dimensional changes so that the top, after sealing, may be folded down into a flattened condition and secured, in one embodiment; in a second embodiment, the container top is slanted, when sealed, and then folded down into a flattened position, when another container is placed thereon.
In the folded down, flat top and slant top containers, and even on occasion in the upright gable top containers, a problem has developed with top leakage occurring because of delamination of the internally located side seam flap. Specifically, in the commercially known smaller cross section containers, that is, the so-called "mini" sizes and in the standard quart sizes, the side seam flap that is secured to the inner surface of the container has a raw edge which is exposed to the interior of the container and is folded in opposite directions. Internal delamination of the paperboard generally occurs in that portion of the side seam flap attached to the triangular end panel, since it is stretched and folded in opposite directions on its fold lines or scores; these fold lines coincide with those which define the attached triangular end panel. Because of the stretching, delamination of the side seam flap also can extend a distance above and below the fold lines. Delamination of the paperboard results in penetration of the enclosed liquid and subsequent leaking and softening of the carton in this area.
Because the larger sizes, namely, the gallon and half gallon sizes, are formed in a different way, the side seam flaps are not specifically susceptible to delamination and top leakage in these sizes.
Although the top leakage problem can occur in the conventional gable top construction, delamination of the side seam flap is much more pronounced when the top is completely or partially folded down as in the flat or slant top configuration. Further, when the top is completely or partially folded down, the delaminated edge of the side seam flap is brought into closer relationship with the upper surface of the milk or other liquid contained within the container. Thus, the flat top and slant top containers formed in this manner are exceptionally susceptible to top leakage problems.
Although this delamination problem can, conceivably, be handled in various ways, it is considered important that the problem be solved in a simple way which involves minimal changes both in the cutting and scoring of the carton blanks and in the formation of the carton blanks into erected containers.